Shadow mask mounting system for color kinescope including one side direct connection

ABSTRACT

A shadow mask is mounted within the faceplate panel of a cathode ray tube for color television at the top and at each side. One of the side mountings is a direct, connection which is nonresilient in a horizontal direction and formed by a bracket fixed to the shadow mask frame and defining a socket for interlocking with the side mounting stud. In one embodiment, this direct connection prevents a lateral motion of the shadow mask frame relative to the faceplate panel while permitting removal of the shadow mask by movement axially of the frame. The top and other side connections are resilient connections, and they are designed to permit a predetermined hinging motion of the shadow mask as it heats up for rotating the mask about the direct connection toward the viewing area thereby correcting for misregistration of the shadow mask apertures with their associated phosphor dot pattern as the shadow mask expands. In one embodiment, the mounting system both rotates and translates the mask toward the screen for correcting for misregistration.

' United States Patent [72] Inventors Irving Weinberg;

Laszlo Javorik, Chicago, Ill.; Eugene V. Heitlinger, Franklin Park, Ill.

[21 Appl. No. 672,474

[22] Filed Oct. 3, I967 [45] Patented Feb. 9, I971 [73] AssigneeNational Video Corporation Chicago, III.

a corporation of Illinois [54] SHADOW MASK MOUNTING SYSTEM FOR COLORKINESCOPE INCLUDING ONE SIDE DIRECT CONNECTION 4 Claims, 6 Drawing Figs.

[52] U.S.Cl 313/85, 313/284 [SI] Int. Cl H01] 1/96, I-IOI j 29/06 [50]Field of Search 3 I 3/92S,

[56] References Cited UNITED STATES PATENTS 3,334,259 8/1967 Shrader 3 l3/85 Primary ExaminerR0y Lake Assistant Examiner-V. LafranchiAttorneyDawson, Tilton, Fallon & Lungmus ABSTRACT: A shadow mask ismounted within the faceplate panel of a cathode ray tube for colortelevision at the top and at each side. One of the side mountings is adirect connection which is nonresilient in a horizontal direction andformed by a bracket fixed to the shadow mask frame and defining a socketfor interlocking with the side mounting stud. In one embodiment, thisdirect connection prevents a lateral motion of the shadow mask framerelative to the faceplate panel while permitting removal of the shadowmask by movement axially of the frame. The top and other sideconnections are resilient connections, and they are designed to permit apredetermined hinging motion of the shadow mask as it heats up forrotating the mask about the direct connection toward the viewing areathereby correcting for misregistration of the shadow mask apertures withtheir associated phosphor dot pattern as the shadow mask expands. In oneembodiment, the mounting system both rotates and translates the masktoward the screen for correcting for misregistration.

PATENTED FEB 9197i INVENTORSZ, IRVING WEINBERG LASZLO JAVORIK EUGENE V.HEITLINGER ATT'YS SHADOW MASK MOUNTING SYSTEM FOR COLOR KINESCOPEINCLUDING ONE SIDE DIRECT CONNECTION BACKGROUND The present inventionrelates to a color television kinescope of the kind which employs ashadow mask; more particularly, it relates to a three-point suspensionsystem for mounting the shadow mask within the peripheral flange of thefaceplate panel.

In shadow mask cathode ray tubes of the kind with which the presentinvention is concerned, three electron beams are deflected across theviewing area or screen in a raster. Three separate sets of phosphor dotsare deposited on the screen and each set of dots produces an image of adifferent primary color when excited by its associated electron beam.Each of the electron beams is modulated by a video signal representativeof one of the three color components. The three resulting images are soclosely spaced that they appear as one on the screen. Desired colors inthe image are produced by excitement of the different phosphors at eachincremental area of the reproduced image.

An apertured shadow mask is placed adjacent the phosphor pattern on thescreen for selective excitation of the dots. The mask has the order of300,000 apertures. Each of the apertures is associated with one set ofthree (i.e. one of each'colorproducing phosphor), or triad of thephosphor dots, and the' beams are so focused that the angle by whicheach beam passed through the mask aperture causes the beams to crosswhile passing through the aperture and separate whereby each beamimpinges only on its associated phosphor dot to the exclusion of theadjacent dots. It is obvious that extreme precision is required in theconstruction of the tube and in the mounting of the shadow mask withinthe tube so that the electron beams do not impinge on dots associatedwith different color since this would generate incorrect color.

During operation, the mask has a greater expansion than the faceplatepanel; hence, there must be some allowance for this expansion in themounting system. By using a resilient or spring mounting system, thisproblem can be overcome.

Normally, the dots are deposited in three separate operations before thefunnel portion of the tube is bonded to the faceplate panel. After eachexposure of the panel to act inic light, the shadow mask must be removedfor a washing.

Since the shadow mask is repeatedly inserted and removed in thefaceplate panel of the cathode ray tube during the manufacturingprocess, not only must the connections between the shadow mask and thefaceplate panel be such that the shadow mask may be easily removed, butit is highly desirous that these connections be almost inflexible sothat proper alignment of apertures with their triads may be repeatedlyachieved. This, however, does not solve the unequal expansion problem.Normally the faceplate panel is arranged in a horizontal position duringthe deposition of the phosphor dots, whereas during normal operation itis arranged in a vertical or standing position. Hence, any sag of thefaceplate panel under its own weight will either in the horizontal orthe vertical position will produce errors inthe ultimate image.

Another more critical problem in locating the mask is that of residualdeformation of the springs when they are subjected to high temperatureduring tube processing.

In the past, all of these requirements have militated against a commonsolution. Prevailing commercial mounting system use either athree-connection or a four-connection system. Some of these systemsinterpose flat steel springs between the shadow mask frame and theperipheral flange on the faceplate paneL. Such mountings have nottotally eliminated the problem of sag; and even the employment ofheavier material for the steel springs have not completely overcome theproblem of residual defonnation.

Although it provides a more rigid mounting, the four-point suspensionsystem requires a custom welding of at least one spring connection. Thethree-point system, while avoiding the need for custom welding, is lessstable. It will be appreciated that usually in the three-point system,there is a top connection which is centered and two side connectionswhich are located below the horizontal center of the mask.

Thus in the three-point system, any change in the applied force ofeither of the side springs will produce a bending moment in the masktending to rotate it about the axis of the tube since there is only asecond-order retaining effect in this type of system, as distinguishedfrom the four-point system.

Aside from the fact that a permanent connection between the shadow maskand the faceplate panel is not feasible because of the removalrequirement, it is also known that the shadow mask becomes heated duringoperation as the scanning electron beams impinge on the shadow mask. Thetemperature of the shadow mask during normal operation will rise to 2030 C. above that of the faceplate panel; and during processing the risewill be 430 C. At the high processing temperature, the change in forcein the side springs produces a coupling moment in the screen to cause aslight rotation and thus a misregistration when in normal operation.

SUMMARY The present invention employs one direct, nonresilient sideconnection between the shadow mask frame and the faceplate panel at theside of the shadow mask. As used herein, the phrase direct connection"means that there is no intervening mounting spring so that once theconnector is seated on the stud, the mask cannot be urged closer to thestud. This direct connection takes the form of a collar or socket fixedto the shadow mask frame and defining an aperture for receiving themounting stud on the side of the faceplate flange.

The other side connection is spring connection using a flat steel springwhich facilitates removal of the shadow mask from the faceplate paneland allows expansion; and this connection preferable employs means fordisplacing the shadow mask relative to the screen when heated by hingingit about the direct connection. This compensates for the partly linear,partly radial expansion of the mask due to heating.

The top connection between the flange and the shadow mask frame issimilar to the side connection except that the allowed motion issomewhat less to correlate with the hinging action of the sideconnection except that the allowed motion is somewhat less to correlatewith the hinging action of the side connection.

With this improved mounting, it has been found that the suspension ofthe shadow mask within the faceplate panel is at least as rigid as if afour-point connection were employed. Further, compensation formisregistration is accomplished, while allowing easy removal of theshadow mask from the faceplate panel.

Other features and advantages of the instant invention will be obviousto persons skilled in the art from the following detailed description ofpreferred embodiments accompanied by the attached drawing; whereinidentical reference numerals will refer to like parts in the variousviews.

THE DRAWING FIG. 1 is a rear elevation of a shadow mask mounted within afaceplate panel;

FIG. 2 is a side view of a conventional mounting using a flat steelspring;

FIG. 3 is a closeup view of the direct side connection between thefaceplate panel and the shadow mask frame;

FIG. 4 illustrates the hinging motion of the shadow mask about thedirect side connection as the'shadow mask expands due to heating; and

FIGS. 5-6 illustrate an alternate embodiment of the direct sideconnection.

DETAILED DESCRIPTION Referring then to the drawing, and particularly toFIGS. I and 2, a faceplate panel is generally designated 10; and itincludes a curved viewing area I1 and an integral, peripheral flange 12which extends toward the rear or constricted neck portion of the tube(not shown) for attachment to the funnel of the tube.

The phosphor dot pattern is deposited on the inside of the curvedportion 11 as at 13 (FIG. 2). This defines the screen or viewing area.

Adjacent the screen is an apertured shadow mask I which generallyconforms to the concave contour of the front panel 11. A heavier, rigidframe 16 is attached about the periphery of the shadow mask 15 formounting to the faceplate panel 10.

In the illustrated embodiment, there are three connections between theshadow mask frame 16 and the peripheral flange 12 of the faceplate paneland these include a first side connection generally designated 17, asecond side connection generally designated 18, and a top connection 19.At each of these connections 17- 19, a mounting stud is embedded in theflange 12. These studs are designated respectively 20, 21, and 22.

In FIG. 2, the connector I8 is seen in more detail as comprising firstand second arched arms 25 and 26 welded at top and bottom to the frame16. The arms 25 and 26 are curved toward the viewing area or front ofthe tube. A crossbar 27 is fastened between the center portions of thearms 25 and 26, and a tab 28 in the form of a flat steel spring isconnected to the crossbar 27. The spring 28 has an aperture 29 forfitting over the side stud 21.

More detail on the side fitting 18 as well as the top connection 19 canbe obtained from the copending, coowned application of Schwartz andJavorik for COLOR TELEVISION TUBE MASK MOUNTING, US Pat No. 3,999,3l9,issued Aug. 27, 1968. It will be noted that as the shadow mask frameheats up, the arms 25 and 26 (composed of metal having a coefficient ofthermal expansion less than that of the metal frame 16) will straightenout as the shadow mask is heated thereby translating the edge of frame16 toward the screen. Alternatively, bimetal mounting means may be usedat the connections 18 and 19 for shifting the mask as its temperaturerises.

The connection 19 which couples the top of the shadow mask to the flangeI2 is similar to the side connection 18 but is slightly modified toallow approximately one-half of the total movement as that of the sideconnection 18, for reasons explained below.

Referring now to FIG. 3, the direct side connection 17 is shown in moredetail. As can be seen therein, the conventional mounting stud 20projects inward of the flange of the faceplate panel, and it defines aslight taper or conical sidewall 32 which is truncated. Welded to theouter side of the frame 16 of the shadow mask is a base or mountingplate 33 to which is fastened a U-shaped channel member 34 having aaperture or socket 35 for receiving the stud 20. It will be appreciatedthat the socket 35 interlocks with the mounting stud 20 to prevent aradial or lateral motion of the cap 34 relative to the mounting stud 20.At the same time, however, the shadow mask may be easily removed fromthis interlocked connection by depressing the mounting springs at theconnections 18 and 19, and with a slight lateral motion combined with alittle tuming, the shadow mask is simply and easily removed from thefaceplate panel. It will be appreciated that with this direct connectionat 17, incremental variances in the force applied by the spring at 18will not affect the mask since there is no play or resiliencytransversely of the axis of the tube at the direct connection.

In addition to the facility of removing the shadow mask from thefaceplate panel, the direct connection I7 allows a slight rotation orhinging of the shadow mask relative to the screen [3. As illustratedmost clearly in FIG. 4 by the dotted line designated as the shadow maskis expanded both radially and linearly due to the impinging electronbeams, the shadow mask 15 will rotate toward the screen I3 forcorrecting misregistration. This is illustrated in the drawing byreference to the single aperture 36 (exaggerated for purposes ofillustration) in the shadow mask 15 which, if the hinging effeet werenot available would move laterally to the right; and in this case it ishinged or rotated slightly forward and takes the position 36' whichcompensates for misregistration.

With this inventive mounting of the mask, it has been observed that theshift of the mask under its own weight is approximately 0.001 in.,whereas with an older type of flat steel spring the sag was close to0.005 in., and even with a more rigid and heavy spring, the sag was upto 0.002 in., which is an appreciable amount of relative movementconsidering the diameter of the apertures, it being greater than [0percent of the diameter.

As an example for the specific case for a 25 inch tube, the cyclelengths for bimetal compensation are as follows: at the connection I9,the cycle length is 0.350 in., for the connection at 18, the cyclelength is 0.473 in.

Referring now to FIGS. 5-6, there is illustrated an alternate form forthe direct side connection I7 which accomplished both the hinging actionheretofore mentioned and, in addition, translates the side of the framewhich receives the direct connection toward the screen. The previouslydescribed suspension system wherein there was compensation only at thecenter of the mask and at the far end of the mask, provided compensationonly along the major axis of the tube; and it does not compensateagainst the expansion along the minor axis. Better compensation may beaccomplished by the arrangement illustrated in FIGS. 5-6 which addscompensation at the direct side connection.

As seen most clearly in FIG. 6, which is a side view of the directconnector, first and second parallel bimetal strips 50 and 51 arecoupled together in spaced relation by means of first and secondU-shaped spacers 52 and 53, the bases of which are welded to the side ofthe frame I6. The bimetal strips 50 and 51 normally extend in a verticaldirection, and each consists of three separate sections, designatedrespectively as 50a, 50b, 50c, and 51a, 51b, and 51c. A third U- shapedspacer 55 is fixed between'the strips 50 and 51 with its base extendingabove them. The spacer 55 has an aperture 56 which receives the stud20'. This structure forms a socket for the direct connection.

The composition and structure of each of these strips is more fullydisclosed in the copending, coowned application of Schwartz and .lavorikfor SUSPENSION SYSTEM FOR COLOR TELEVISION TUBE MASK, US. Pat. No.3,449,61 l,issued Jun. I0, I969.

Each of the sections comprising the strips 50 and SI is composed ofabimetal pair having different coefficients of thermal expansion. In theillustration, the metal having the larger coefficient of expansion isshown as having a greater thickness; and the center sections 50b and 51bare in reversed position relative to their end sections.

Thus, the bimetal strips 50 and 51 are designed to assume the curvedshapes respectively designated 50'- and 51 for moving the socket 55rearward of the fixed mounting 52 and 53. Since the stud 20 is receivedin the aperture 56, this effect moves the shadow mask forward toward thescreen.

By providing for a temperature-sensitive connection at both sideconnections and at the top connection, compensation for misregistrationis made along both the major and the minor axes of the tube. For thisparticular arrangement, and for a 25- inch television tube, the cyclelength of the bimetal at the mounting location 17 is 0.175 in., thecycle length at mounting location I9 is 0.315 in., and the cycle lengthhas been calculated to give a movement that effects compensation at thehalf-length of the minor axis thereby cutting the misregistration at theend in half and distributing the error evenly between the end point andthe center point.

With these arrangements it can be seen that for any changes in the forceof the spring 28 at the right side of the tube (as viewed in FIG. 1)there will be no corresponding moment coupled to the mask even thoughthe spring may be heated substantially as during processing.

Having thus described in detail preferred embodiments of the invention,it will be obvious to persons skilled in the art that certain structuralelements may be modified or replaced by equivalent components; and it istherefore intended that all such substitutions and modifications becovered as they are embraced within the spirit and scope of the appendedclaims.

We Claim:

1. In a color television tube including a faceplate panel defining aviewing screen and a peripheral flange depending from said screen andhaving only a top and first and second side mounting studs extendingradially of said tube, and further including shadow mask means, athree-point mounting system incorporated into said mask meanscomprising: a mask defining apertures in register with the phosphor dotpattern on said screen; a frame secured to the periphery of said mask;means defining a socket radially fixed to one side of said frame forreceiving and interlocking with said first side stud of said flange,said socket means and said stud cooperating to form a direct connectionthereby preventing relative lateral movement between said frame and saidflange while permitting said frame to be removed by motion radial ofsaid tube; first resilient means mounted on the top of said frame forresiliently coupling to said top mounting stud on said flange; andsecond resilient means on the other side of said frame for resilientlycoupling to said second stud of said flange.

2. The structure of claim 1 further comprising means associated withsaid second resilient coupling means and said top resilient couplingmeans for rotating said mask bodily toward said viewing area in responseto temperature increase about said direct connection.

3. The structure of claim 1 wherein said side resilient mounting meansincludes flat steel spring means permitting movement of said maskrelative to said screen as the temperature of said mask rises, and meansassociated with said top resilient mounting means permitting movement ofthe top of said frame relative to said screen, the movement of said sidebeing greater than that at said top.

4. The structure of claim 2 further comprising temperaturesensitivemeans associated with said socket means for moving said frame towardsaid screen in response to a predetermined temperature rise whereby saidmask is both rotated and translated toward said screen in correcting formisregistration.

1. In a color television tube including a faceplate panel defining aviewing screen and a peripheral flange depending from said screen andhaving only a top and first and second side mounting studs extendingradially of said tube, and further including shadow mask means, athree-point mounting system incorporated into said mask meanscomprising: a mask defining apertures in register with the phosphor dotpattern on said screen; a frame secured to the periphery of said mask;means defining a socket radially fixed to one side of said frame forreceiving and interlocking with said first side stud of said flange,said socket means and said stud cooperating to form a direct connectionthereby preventing relative lateral movement between said frame and saidflange while permitting said frame to be removed by motion radial ofsaid tube; first resilient means mounted on the top of said frame forresiliently coupling to said top mounting stud on said flange; andsecond resilient means on the other side of said frame for resilientlycoupling to said second stud of said flange.
 2. The structure of claim 1further comprising means associated with said second resilient couplingmeans and said top resilient coupling means for rotating said maskbodily toward said viewing area in response to temperature increaseabout said direct connection.
 3. The structure of claim 1 wherein saidside resilient mounting means includes flat steel spring meanspermitting movement of said mask relative to said screen as thetemperature of said mask rises, and means associated with said topresilient mounting means permitting movement of the top of said framerelative to said screen, the movement of said side being greater thanthat at said top.
 4. The structure of claim 2 further comprisingtemperature-sensitIve means associated with said socket means for movingsaid frame toward said screen in response to a predetermined temperaturerise whereby said mask is both rotated and translated toward said screenin correcting for misregistration.